The present invention addresses the issues related to consistently and accurately retaining a plurality of disposable ink jet pens in a pen receiving socket of a multi-head reciprocating carriage assembly. Many approaches of securing disposable ink jet pens have been tested and tried over the years and the driving concern has often been ease of use by the end user or operator of the print engine. Thus, while convenience in operation is required for consumer acceptance, as more and more ink jet pens have been added to ink jet print engines the difficulty in assembling the carriage and its associated pen retaining features have increased while at the same time the overall complexity of the pen retaining sockets and the carriage assembly itself have greatly increased.
In addition, an ever increasing variety of specialized ink jet printing substrates have been developed for a number of new niche markets, for example such as the so-called `fine art` market characterized by relatively thick and non-compliant media. These new types of media often require specialized ink jet ink formulations for durability, light-fastness, and color fidelity all of which are improved when a common, optimum spacing between the ink emitting nozzles and the ink receiving surface of the media is maintained during printing operations. Accordingly, a need exists for ink print engines that can readily adapt to media of differing thickness as well as those print engines that have simple procedures for removing and accurately replacing ink jet pens with other ink jet pens containing, for example, new specialized formulations of ink jet ink. A need exists in the prior art to thus simplify the operation of changing ink jet pens, not only when faulty or expired, but also for convenience and so that the operator can utilize the vast variety of new ink formulations available now and in the future as well as rapidly re-set the spacing between the ink emitting nozzles and the printing substrate. Finally a need exists in the art to simplify assembly of the pen retaining sockets of the carriage assembly, and to reduce the number of parts and complexity of assembling a carriage assembly having a vertical adjustment relative to the printing substrate.